1. Field of the Invention
This invention relates to gas lasers in general, and to an improved gas laser with improved cooling apparatus, in particular.
2. Prior Art
There are several known designs according to which gas lasers such as the carbon dioxide laser can be constructed. In each of these designs an electrical discharge is passed through a static gas in a "gas discharge tube". The simplest and lowest power approach utilizes a water-cooled gas discharge tube. That is, a jacket for flowing water is placed at the gas discharge tube to provide temperature control. This approach is currently used in the vast majority of commercial CO.sub.2 lasers sold today. However, this approach has an output power limitation. This power limitation arises because the gas temperature in a CO.sub.2 laser cannot exceed approximately 300.degree. C. without detrimental effects. Because the electrical discharge is continuously heating the gas, there is a maximum input power per unit length which is determined by the thermal conductivity of the gas. This maximum input power is about 350 watts per meter of discharge length, thereby producing a maximum output beam power of approximately 70 watts per meter of length.
Another approach to the construction of CO.sub.2 lasers is generally called the convective flow lasers. In this approach, gas is circulated through an electrical discharge region where the electrical discharge excites the molecules thereby producing laser action. The gas is then flowed to a cooling section where the waste heat is removed from the gas. The convective flow lasers do not have any specific limitation as to the output power per unit length, inasmuch as this is dependent on variables such as the gas flow speed, gas pressure, and the like.
Other laser designs such as gas dynamic lasers and the like will not be discussed further, because they do not have application to the present design.
The gas discharge tube laser design has the advantages that the long, narrow discharge geometry allows good laser beam quality (TEM.sub.00 modes) and the gas can be flowed through the laser discharge region at a slow flow rate. However, the major disadvantage of the discharge tube design is its power limitation.
The convective flow lasers have no specific power limitation, but they have the disadvantages that the electrical discharges can go unstable and cause the laser to be sufficiently unreliable that it is undesirable for many industrial applications, the geometry of the discharge region dictated by the conventional flow laser designs is not conducive to producing good laser beam mode quality, and vast quantities of gas have to be pumped by high-speed and expensive pumps.